[core] move framebuffer reading to gl::Context

5 files changed, 48 insertions, 49 deletions

diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 1cd546f407..811a038caf 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -92,6 +92,32 @@ UniqueRenderbuffer Context::createRenderbuffer(const RenderbufferType type, cons
     return renderbuffer;
 }
 
+std::unique_ptr<uint8_t[]> Context::readFramebuffer(const Size size, const TextureFormat format, const bool flip) {
+    const size_t stride = size.width * (format == TextureFormat::RGBA ? 4 : 1);
+    auto data = std::make_unique<uint8_t[]>(stride * size.height);
+
+#if not MBGL_USE_GLES2
+    // When reading data from the framebuffer, make sure that we are storing the values
+    // tightly packed into the buffer to avoid buffer overruns.
+    pixelStorePack = { 1 };
+#endif // MBGL_USE_GLES2
+
+    MBGL_CHECK_ERROR(glReadPixels(0, 0, size.width, size.height, static_cast<GLenum>(format),
+                                  GL_UNSIGNED_BYTE, data.get()));
+
+    if (flip) {
+        auto tmp = std::make_unique<uint8_t[]>(stride);
+        uint8_t* rgba = data.get();
+        for (int i = 0, j = size.height - 1; i < j; i++, j--) {
+            std::memcpy(tmp.get(), rgba + i * stride, stride);
+            std::memcpy(rgba + i * stride, rgba + j * stride, stride);
+            std::memcpy(rgba + j * stride, tmp.get(), stride);
+        }
+    }
+
+    return data;
+}
+
 namespace {
 
 void checkFramebuffer() {
diff --git a/src/mbgl/gl/context.hpp b/src/mbgl/gl/context.hpp
index 9bfa54fa55..169aa5566e 100644
--- a/src/mbgl/gl/context.hpp
+++ b/src/mbgl/gl/context.hpp
@@ -62,6 +62,15 @@ public:
                                   const Renderbuffer<RenderbufferType::DepthStencil>&);
     Framebuffer createFramebuffer(const Texture&);
 
+    template <typename Image,
+              TextureFormat format = Image::channels == 4 ? TextureFormat::RGBA
+                                                          : TextureFormat::Alpha>
+    Image readFramebuffer(const Size size, bool flip = true) {
+        static_assert(Image::channels == (format == TextureFormat::RGBA ? 4 : 1),
+                      "image format mismatch");
+        return { size, readFramebuffer(size, format, flip) };
+    }
+
     // Create a texture from an image with data.
     template <typename Image>
     Texture createTexture(const Image& image, TextureUnit unit = 0) {
@@ -167,6 +176,7 @@ private:
     void updateTexture(TextureID, Size size, const void* data, TextureFormat, TextureUnit);
     UniqueFramebuffer createFramebuffer();
     UniqueRenderbuffer createRenderbuffer(RenderbufferType, Size size);
+    std::unique_ptr<uint8_t[]> readFramebuffer(Size, TextureFormat, bool flip);
 
     PrimitiveType operator()(const Points&);
     PrimitiveType operator()(const Lines&);
diff --git a/src/mbgl/gl/types.hpp b/src/mbgl/gl/types.hpp
index 6e1bc5f8e1..1697656469 100644
--- a/src/mbgl/gl/types.hpp
+++ b/src/mbgl/gl/types.hpp
@@ -50,6 +50,10 @@ enum class TextureWrap : bool { Clamp, Repeat };
 enum class TextureFormat : uint32_t {
     RGBA = 0x1908,
     Alpha = 0x1906,
+#if not MBGL_USE_GLES2
+    Stencil = 0x1901,
+    Depth = 0x1902,
+#endif // MBGL_USE_GLES2
 };
 
 enum class PrimitiveType {
diff --git a/src/mbgl/renderer/painter_debug.cpp b/src/mbgl/renderer/painter_debug.cpp
index bdc0b90bd4..dfb1581bab 100644
--- a/src/mbgl/renderer/painter_debug.cpp
+++ b/src/mbgl/renderer/painter_debug.cpp
@@ -68,29 +68,16 @@ void Painter::renderClipMasks(PaintParameters&) {
     context.program = 0;
 
 #if not MBGL_USE_GLES2
-
-    // When reading data from the framebuffer, make sure that we are storing the depth values
-    // tightly packed into the buffer to avoid buffer overruns. Also see unpacking adjustment below.
-    context.pixelStorePack = { 1 };
-
     // Reset the value in case someone else changed it, or it's dirty.
     context.pixelTransferStencil = gl::value::PixelTransferStencil::Default;
 
     // Read the stencil buffer
     const auto viewport = context.viewport.getCurrentValue();
-    auto pixels = std::make_unique<uint8_t[]>(viewport.size.width * viewport.size.height);
-    MBGL_CHECK_ERROR(glReadPixels(
-                viewport.x,           // GLint x
-                viewport.y,           // GLint y
-                viewport.size.width,  // GLsizei width
-                viewport.size.height, // GLsizei height
-                GL_STENCIL_INDEX,     // GLenum format
-                GL_UNSIGNED_BYTE,     // GLenum type
-                pixels.get()          // GLvoid * data
-                ));
+    auto image =
+        context.readFramebuffer<AlphaImage, gl::TextureFormat::Stencil>(viewport.size, false);
 
     // Scale the Stencil buffer to cover the entire color space.
-    auto it = pixels.get();
+    auto it = image.data.get();
     auto end = it + viewport.size.width * viewport.size.height;
     const auto factor = 255.0f / *std::max_element(it, end);
     for (; it != end; ++it) {
@@ -101,7 +88,7 @@ void Painter::renderClipMasks(PaintParameters&) {
     context.rasterPos = { -1, -1, 0, 1 };
     context.pixelStoreUnpack = { 1 };
     MBGL_CHECK_ERROR(glDrawPixels(viewport.size.width, viewport.size.height, GL_LUMINANCE,
-                                  GL_UNSIGNED_BYTE, pixels.get()));
+                                  GL_UNSIGNED_BYTE, image.data.get()));
 #endif // MBGL_USE_GLES2
 }
 
@@ -112,11 +99,6 @@ void Painter::renderDepthBuffer(PaintParameters&) {
     context.program = 0;
 
 #if not MBGL_USE_GLES2
-
-    // When reading data from the framebuffer, make sure that we are storing the depth values
-    // tightly packed into the buffer to avoid buffer overruns. Also see unpacking adjustment below.
-    context.pixelStorePack = { 1 };
-
     // Scales the values in the depth buffer so that they cover the entire grayscale range. This
     // makes it easier to spot tiny differences.
     const float base = 1.0f / (1.0f - depthRangeSize);
@@ -124,23 +106,14 @@ void Painter::renderDepthBuffer(PaintParameters&) {
 
     // Read the stencil buffer
     auto viewport = context.viewport.getCurrentValue();
-    auto pixels = std::make_unique<uint8_t[]>(viewport.size.width * viewport.size.height);
-
-    MBGL_CHECK_ERROR(glReadPixels(
-                viewport.x,           // GLint x
-                viewport.y,           // GLint y
-                viewport.size.width,  // GLsizei width
-                viewport.size.height, // GLsizei height
-                GL_DEPTH_COMPONENT,   // GLenum format
-                GL_UNSIGNED_BYTE,     // GLenum type
-                pixels.get()          // GLvoid * data
-                ));
+    auto image =
+        context.readFramebuffer<AlphaImage, gl::TextureFormat::Depth>(viewport.size, false);
 
     context.pixelZoom = { 1, 1 };
     context.rasterPos = { -1, -1, 0, 1 };
     context.pixelStoreUnpack = { 1 };
     MBGL_CHECK_ERROR(glDrawPixels(viewport.size.width, viewport.size.height, GL_LUMINANCE,
-                                  GL_UNSIGNED_BYTE, pixels.get()));
+                                  GL_UNSIGNED_BYTE, image.data.get()));
 #endif // MBGL_USE_GLES2
 }
 #endif // NDEBUG
diff --git a/src/mbgl/util/offscreen_texture.cpp b/src/mbgl/util/offscreen_texture.cpp
index 6352e38ab7..aad20e59d3 100644
--- a/src/mbgl/util/offscreen_texture.cpp
+++ b/src/mbgl/util/offscreen_texture.cpp
@@ -1,6 +1,5 @@
 #include <mbgl/util/offscreen_texture.hpp>
 #include <mbgl/gl/context.hpp>
-#include <mbgl/gl/gl.hpp>
 
 #include <cstring>
 #include <cassert>
@@ -29,20 +28,7 @@ gl::Texture& OffscreenTexture::getTexture() {
 }
 
 PremultipliedImage OffscreenTexture::readStillImage() {
-    PremultipliedImage image { size };
-    MBGL_CHECK_ERROR(
-        glReadPixels(0, 0, size.width, size.height, GL_RGBA, GL_UNSIGNED_BYTE, image.data.get()));
-
-    const auto stride = image.stride();
-    auto tmp = std::make_unique<uint8_t[]>(stride);
-    uint8_t* rgba = image.data.get();
-    for (int i = 0, j = size.height - 1; i < j; i++, j--) {
-        std::memcpy(tmp.get(), rgba + i * stride, stride);
-        std::memcpy(rgba + i * stride, rgba + j * stride, stride);
-        std::memcpy(rgba + j * stride, tmp.get(), stride);
-    }
-
-    return image;
+    return context.readFramebuffer<PremultipliedImage>(size);
 }